The starting SBS has very little to do with arm safety. If you have deformed the string to the point where it stops stretching, the dynamic response of the stringbed will absorb much less energy from ball impact. Assuming you strike the ball with the same force, where is all that energy going? There aren't very many places, I can assure you.

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The energy goes into the deformation of the stringbed. Look at the definition of SBS.

You are confounding elasticity with elongation here. Less deformation in the perpendicular plane of the string bed (the elastic elongation) doesn't have much to do with string tension or the ability to hold it.

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Elasticity is the only thing that holds the tension of the string and the stringbed.
Lets take 2 examples:
- take a string that has NO elongation when stressed. You stress at 30kg's, clamp, and what happens? No tension in the string
- take a string without elasticity, and just some creep: tension at 30kg's, the string will deform, and after releasing the tension, the deformation is still there. So if you use this string, you will not be able to give this string any tension.

. If you tension a string for 1 year anc come back it will have reached the point of no return and may have actually broken the string.

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In my string-tension-experiment I left the string under 50kg tension all night. I did the 4th set of measurements this morning, no problems. The retensioned again at 50kg's. When I came back after a few hours the string had broken.....

.Put another way, I trust the Babolat engineers to not skip a simple manufacturing process that would better xcel elasticity maintenance and therefore decide to mess with their designed product in my garage..... a man must know his own limitations and all that.

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You can buy a lot of pre-stretched strings, eg Luxilon/Kirschbaum. They all sell with the argument: better tension-maintenance

All of this is very interesting reading to me even though I am perfectly happy with the results I'm getting with my LO machine ... which is really all that matters at the end of the day. As long as the player's using the racquets I string are happy, then I'm happy.

Anyway, I'm interested in any opinions with regard to the following ...

As far as I understand, with a LO machine the string is pulled to tension one time and then starts to lose tension when the tensioner locks out until the string is clamped and any slippage ceases. With a CP machine, the string is pulled to tension, starts to lose tension, is pulled to tension again, starts to lose tension, is pulled to tension again, etc. etc. until the desired tension is achieved and stabilised. Then the string is clamped.

So with a LO machine, the string is "stressed" one single time. With a CP machine, the string can be "stressed" several times. Now, while I understand that the point of the exercise is to achieve relatively consistent tension for each string, I wonder whether stressing multiple strings, multiple times has any negative impact on the string bed compared to stressing multiple strings a single time?

I would think that pulling each string to tension a single time is better than pulling it multiple times regardless of the fact that string is "elastic".

I
Regardless of the science behind what happens to the string as tension is lost, the point is that not everyone has identical criteria for optimal playability. It's OK to disagree in this case as long as we can all agree on that fact It's complicated, and that's why i personally find this interesting.

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@diredesire, indeed not everyone has identical criteria for optimal playability which then makes any general criteria somewhat moot as far as I'm concerned. It is pretty much all subjective and no amount of "science" is going to make it otherwise - until such time that someone develops the perfect string that everyone will end up using.

So taking that position, the whole string thing is not that complicated to me. What can be complicated is understanding each player's individual preferences and then providing them with a solution that meets their individual needs as closely as possible. Some would argue this has a lot less to do with the science of tennis strings and stringing technique, and a lot more to do with human psychology

You can buy a lot of pre-stretched strings, eg Luxilon/Kirschbaum. They all sell with the argument: better tension-maintenance

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I don't doubt that you can improve tension maintenance; just not convinced that's the real end goal. My question is how to best keep strings feeling fresh and elastic. Sure it's somewhat related to tension but think there is more to it.

As you can see, the "pre-stretch" eliminates a lasting elongation of 2.4%. The pre-stretched string still has elasticity, and has a "lasting elongation" of 0.29% You get a different string when pre-stretching, for sure, but don't tell me I killed the elasticity!

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The only claim is that you affected elasticity, not that you killed it. No one is suggesting that you reduced elasticity down to 0%. That'd be an insane statement. You affected/changed it from it's "natural" (or conventionally installed) state.

Yes, of course. But at the same reference-tension, and if you use a cp correctly, the tension-loss after clamping the string is marginal compared with a lock-out

Well, you come up with a nice term for elliminating the permanent-elongation ( that part of the elongation that "stays" after you stopp pulling and let the string relax)

Yes, twisted steal wire can act as a "spring". I was referring to "straight forward steel wire" , which can not be used due to lack of elasticity

The energy goes into the deformation of the stringbed. Look at the definition of SBS.

Elasticity is the only thing that holds the tension of the string and the stringbed.
Lets take 2 examples:
- take a string that has NO elongation when stressed. You stress at 30kg's, clamp, and what happens? No tension in the string
- take a string without elasticity, and just some creep: tension at 30kg's, the string will deform, and after releasing the tension, the deformation is still there. So if you use this string, you will not be able to give this string any tension.

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I take issue with the "correctly" assertion - this is an opinion, and again - it depends on your goals. If a tensioner has come to a (reasonable/satifactory) "resting" state, it isn't an incorrect technique.

You can use a straight forward steel wire if you so desire, there's no limiting reason why you couldn't. I would even go as far as to say that I believe you are looking for low amounts of elongation and aren't pursuing the tension maintenance as much as you (and ricardo) suggest. My concern here is there is a false equivalency between the two that is being made. Low elongation (if we take it to the extreme of a steel wire) would result in a very consistent string bed across the life of the string job. I see very similar desires here from the extreme pre-stretchers. I am also curious if you guys have tracked SBS across the string job life and compared it to a conventional string job.

"Look at the definition of SBS" only suggests to me that you missed my point (again). If you have stretched out any non-permanent elongation from your strings, you have reduced the strings ability to elongate - which would also reduce the ability for the string to deform to the ball. Since the string cannot deform as much, assuming an equal amount of force into the system, where does the energy go? SBS is simply SBS. It doesn't suggest anything about the dynamic deformation of a string bed beyond the standardized test methods - again, there are real-world differences to frames/string beds with the same "starting" SBS. I know you understand that the force requirement is not linear, I've seen you post on it before!

Your examples are misleading, as they aren't reproducible in real life. You are correct from a strict 'thought experiment' perspective, but I'm not sure what the point is? (If you tried to measure SBS, it'd be infinity and zero in your examples) Steel strings (solid or not) can still hold tension. They are much, much less elastic than nylon or copolymer strings, but they can still hold tension. Maybe I'M missing the point here. Feel free to educate me.

All of this is very interesting reading to me even though I am perfectly happy with the results I'm getting with my LO machine ... which is really all that matters at the end of the day. As long as the player's using the racquets I string are happy, then I'm happy.

Anyway, I'm interested in any opinions with regard to the following ...

As far as I understand, with a LO machine the string is pulled to tension one time and then starts to lose tension when the tensioner locks out until the string is clamped and any slippage ceases. With a CP machine, the string is pulled to tension, starts to lose tension, is pulled to tension again, starts to lose tension, is pulled to tension again, etc. etc. until the desired tension is achieved and stabilised. Then the string is clamped.

So with a LO machine, the string is "stressed" one single time. With a CP machine, the string can be "stressed" several times. Now, while I understand that the point of the exercise is to achieve relatively consistent tension for each string, I wonder whether stressing multiple strings, multiple times has any negative impact on the string bed compared to stressing multiple strings a single time?

I would think that pulling each string to tension a single time is better than pulling it multiple times regardless of the fact that string is "elastic".

Thoughts?

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Depends on what you want! If you want the "side effects" or systematic benefits of a CP, then that's great! There's no real value (negative or positive) to be placed here. At the end of the day, the systematic difference isn't something we can honestly control for. There are going to be both types of machines in the future, so the difference(s) will always be there.

@diredesire, indeed not everyone has identical criteria for optimal playability which then makes any general criteria somewhat moot as far as I'm concerned. It is pretty much all subjective and no amount of "science" is going to make it otherwise - until such time that someone develops the perfect string that everyone will end up using.

So taking that position, the whole string thing is not that complicated to me. What can be complicated is understanding each player's individual preferences and then providing them with a solution that meets their individual needs as closely as possible. Some would argue this has a lot less to do with the science of tennis strings and stringing technique, and a lot more to do with human psychology

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"Until such time that someone develops the perfect string..." - I'm sure you're not 100% serious about that statement, but if you think this is a possibility, I'd like to point you to this talk, it may change the way you (or others) look at what "best" means. I'm not suggesting this is fact - form your own opinions after watching. https://www.ted.com/talks/malcolm_gladwell_on_spaghetti_sauce?language=en

(IMO, there are differences that can't be completely/truly compensated for, and ... that's OK.)

"Until such time that someone develops the perfect string..." - I'm sure you're not 100% serious about that statement, but if you think this is a possibility, I'd like to point you to this talk, it may change the way you (or others) look at what "best" means. I'm not suggesting this is fact - form your own opinions after watching.https://www.ted.com/talks/malcolm_gladwell_on_spaghetti_sauce?language=en

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"People don't know what they want! ... "The mind knows not what the tongue wants." It's a mystery!"

Yes, of course. But at the same reference-tension, and if you use a cp correctly, the tension-loss after clamping the string is marginal compared with a lock-out

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Again, stating the obvious here...there are different types of machines in existence which set out to achieve the same objective. The implication, that one is somehow better than another, is at odds with the very existence of the different types of machines. If LO machines are inferior, as you seem to suggest, then why are they still manufactured? (Flame suit on, awaiting Steam engine comments).

The relevant point, IMO is that the 2 methods of imparting tension (LO vs CP) are different. The differences between them doesn't equate to one being "bad", and the other "good." Speaking generally, both mechanisms have proven reliable, and practical, as a means to string tennis racquets. To me, that makes both methods, while different, relevant, as a means to achieve the desired objective.

With a CP machine, the string is pulled to tension, starts to lose tension, is pulled to tension again, starts to lose tension, is pulled to tension again, etc. etc. until the desired tension is achieved and stabilised. Then the string is clamped.

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On a CP the string is tensioned with same reference-tension all tensioning-time. In this time, the string stretches (a little bit).

No, I promiss I will never say this (again). A LO is fast, is consistent, is accurate. BUT the simple fact that you go down in tension after lock-out makes it for me more an "art" to string on such a machine. My goal is to controll all aspects of the stringing process, and I think a (e)CP helps (me better as a LO)

Yes, you are right. That is of course the procedure, and that is how I work (and all stringers with an (e)CP. Allthough some seem to clamp "immediately after the beep of the eCP", no waiting for possible stretching of the string.

You are making self-contradiction. Do you wait before clamping or after clamping? If before, do you admit your comment below is wrong?

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I wait before clamping (like all stringers using a (e)CP). And no, there is no "self-contradiction"
The effect of the constant-pull, while waiting, is that the string will loose the (fast) stretch at reference tension. Then you clamp.
On a lock-out, the string is "locked-out" as soon as the reference-tension is reached. Waiting to clamp is useless, the string is already clamped by the lock-out, and your "clamping" action will only isolate a piece of the already clamped string.
So, the (e)CP-method removes the (fast) stretch at reference-tension, the lock-out doesn't. Therefore the string-tension in a lock-out is lower as a (e)CP using the same reference-tension. Of course you can compensate this by using a higher reference-tension at the lock-out.

Who knew that the Dutch could take a stand on anything. Always thought they were nice if sensible/insipid bunch But I've not explored beyond Amsterdam.

Seriously... MathieuR and Ricardo... You can explore pre-stretching, re-sue of strings, etc.. with another thread that's more on topic. The discussion here is way, way beyond Irvin's original post and is just plain extreme thread hijacking.

ok, I'll start a new one (or revive an old one, cause I think there is already one on pre-stretching)
And I will come back on the 'thread-relevant-open-questions". Cause I still think the proposition as given by Irvin in the opening post is "incorrect"

I did do some thinking First, you have to make some assumptions. (if the string is 100% elastic, no permanent elongation, there is will be no difference in this experiment between the 2 pieces of string).
Of course this is a first "rough" approach. I trust this will be improved by fellow-posters.

Assumptions:
1 I take a "creepy" string, that will have at reference-tension of 40kg 10% length increase, of which is 7% "lasting elongation", and 3% elastic elongation. Both the lasting and elastic elongation are linear in the range from 0-40kg "real" tension (so at 20kg there is 5% elongation, of which 3.5% is permanent, and 1.5% elastic; there is 0.175% permanent elongation for every kilo, and 0.075% elastic elongation).
2 the tension in the string is linear with the elasticity/elastic-elongation
2 a tensioned string will loose 10% tension due to "slow creep" in the first 24hours.

So, when I use a CP to give a piece of string 5% elongation, I have to use a reference-tension of 20kg. Length goes from 100% to 105%. After 24hrs tension has dropped to 18kg, remaining elasticity is 0.9*1.5%=1.3%. When you relax the string, length will be 0.987 * 105 = 103.64% of original lenght

The LO, to give 5% elongation. Reference-tension needs to be more as ref.tension of the CP, say +15%, 23kg. This means this piece of string will be "deformed" more, there will be 3 * 0.175% +3.5% = 4.025% permanent elongation. Leaving only 0.875% elastic elongation at lock out. Tension is held by the elastic-elongation, is direct after lock-out 0.875/0.075 = 11.7kg
After 24hrs -10% -> 10.5kg = 0.788% elasticic-elongation
After relaxation length will be 99.212 * 105 = 104.17% of original length.

Of course plenty of holes to shoot . Like to see another "calculation" with new assumptions.

I did do some thinking First, you have to make some assumptions. (if the string is 100% elastic, no permanent elongation, there is will be no difference in this experiment between the 2 pieces of string).
Of course this is a first "rough" approach. I trust this will be improved by fellow-posters.

Assumptions:
1 I take a "creepy" string, that will have at reference-tension of 40kg 10% length increase, of which is 7% "lasting elongation", and 3% elastic elongation. Both the lasting and elastic elongation are linear in the range from 0-40kg "real" tension (so at 20kg there is 5% elongation, of which 3.5% is permanent, and 1.5% elastic; there is 0.175% permanent elongation for every kilo, and 0.075% elastic elongation).
2 the tension in the string is linear with the elasticity/elastic-elongation
2 a tensioned string will loose 10% tension due to "slow creep" in the first 24hours.

So, when I use a CP to give a piece of string 5% elongation, I have to use a reference-tension of 20kg. Length goes from 100% to 105%. After 24hrs tension has dropped to 18kg, remaining elasticity is 0.9*1.5%=1.3%. When you relax the string, length will be 0.987 * 105 = 103.64% of original lenght

The LO, to give 5% elongation. Reference-tension needs to be more as ref.tension of the CP, say +15%, 23kg. This means this piece of string will be "deformed" more, there will be 3 * 0.175% +3.5% = 4.025% permanent elongation. Leaving only 0.875% elastic elongation at lock out. Tension is held by the elastic-elongation, is direct after lock-out 0.875/0.075 = 11.7kg
After 24hrs -10% -> 10.5kg = 0.788% elasticic-elongation
After relaxation length will be 99.212 * 105 = 104.17% of original length.

Of course plenty of holes to shoot . Like to see another "calculation" with new assumptions.

And here you are wrong . I am here to learn, and share experiences. If I have a (bold/insane/..) stand, I am happy when I am corrected when wrong. But then I always need to know the facts/figurs/experiences that demonstrate that I have to accept my stupidity (on that specific subject, not in general )

Could well be that result of a LO and a CP are exactly the same when they string a piece of string 5%.

New approach to calculate the difference between a LO and (e)CP stretched piece of string, both stretched to +5% length, clamped. And after 24 hours both pieces of string are relaxed, and the length is measured.

Assumptions:
1: I take a "creepy" string, that will have at reference-tension of 40kg 10% length increase, of which is 7% "lasting elongation", and 3% elastic elongation. Both the lasting and elastic elongation are linear in the range from 0-40kg "real" tension (so at 20kg there is 5% elongation, of which 3.5% is permanent, and 1.5% elastic; there is 0.175% permanent elongation for every kilo, and 0.075%/kg elastic elongation).
This is the "fast elongation"
If we would tension the string for 24hrs at 40kg, the "slow creep/slow-permanent-elongation" would not be 7%, but 9%. Elastic-elongation at 40kg/24hrs is unchanged, 3%. Total elongation 12%
2: the tension in the string is linear with the elasticity/elastic-elongation

So, when I use a CP to give a piece of string 5% elongation, I have to use a reference-tension of 20kg. Length goes from 100% to 105%. (3.5% lasting-elongation, 1.5% elastic elongation). After 24hrs, the "slow creep" will give a shift. At 20kg/24hrs slow-creep/lasting-elongation would be 4.5%. If the lasting-elongation% goes up, the elastic-elongation% has to go down (lenght stays the same )
Let's assume lasting-elongation% goes from 3.5->3.75%, and the elastic-elongation from 1.5->1.25%.
After 24hrs the tension in the clamped piece of string is now 1.25 / 0.075 = 16.7kg (at 16.7kg the lasting-elongation24hrs% would be 16.7/20 * 4.5 =3.75%)

The LO, to give 5% elongation. Reference-tension needs to be more as ref.tension of the CP, say +15%, 23kg.
In fact the faster you crank, the higher the ref.tension needs to be to get the 5% elongation. (if you crank extremely slow, result is same as CP)
Most of the "fast elongation" will be elastic elongation (if you stretch a string in a split-second, and release it again, the "creep" had "no time")
Elastic elongation will be 1.725%, lasting elongation 3.275% (less as with the CP stretch); this is the "fast stretch"
After clamping and 24hrs waiting, the same math applies as for the CP-situation. A shift from elastic-elongation towards lasting-elongation.
And with the starting-assumptions you will come to exactly the same result.

I wonder when the relation between elastic elongation and permanent elongation is NOT linear with tension, the result would be different. Back to the drawing board, cause I can't believe there is no difference.

EDIT: BUT: you do not tension on length-increase; you tension on "reference-tension". And that is a complete different ballgame.

Sorry to keep this thread going.. let me know if I should move this quoted post over to the new thread - I can do that. I just figured there'd be a ton of discontinuity in discussion. Feel free to un-sub if you are not interested

I have stretched/removed the PERMANENT elongation while pre-stretching. The elastic-elongation is hardly changed

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I'd be curious to see your data as compared to a conventional string job. Before you do this, though, I'd like to see your hypotheses regarding the absolute tension loss of the very stretched string jobs. My hypothesis is that you are losing a lot more tension than you think you are even after this prestretching. The feel might not change as much as compared to a regular string job, but that is a separate phenomenon than tension loss. I think playability arguments are often confounded with tension loss, but playability focused techniques are as interesting (if not moreso!) than tension focused techniques because that is what the player actually experiences.

As far as the permanent elongation comment, please read about material properties before making these claims:http://www.kazuli.com/UW/4A/ME534/lexan2.htm
If you have made any permanent elongation, you have absolutely affected the elastic properties of the string. It is naive (and very misleading!) to make a statement about the elastic elongation being hardly changed. This is for a thick piece of lexan (polycarbonate) plastic, but the principles still apply here.

I'd also like to point out to others to check out the deformation behavior section of the site. It is one reason why the stretch-ad-nauseum approach is an interesting one. Homogeneous materials can have interesting effects when stretched beyond the elastic limit/yield point that can affect playability in a large way. However, this doesn't say anything about preference or absolute "best."

Serious question as I can't find a definitive answer (although I recall reading about this in the past) - do strings really snap back faster than the ball leaves the string? Is a string bed a trampoline or is elasticity a non-factor in true energy return? Is it on the same order of magnitude as a stiff frame?

Is this amount of string deformation really "returning energy" as we think? I swear I saw some high speed footage years ago that suggested that strings do not snap back until after the ball leaves the frame, but I'm not able to find any articles now.

Sorry to keep this thread going.. let me know if I should move this quoted post over to the new thread - I can do that. I just figured there'd be a ton of discontinuity in discussion. Feel free to un-sub if you are not interested

I'd be curious to see your data as compared to a conventional string job. Before you do this, though, I'd like to see your hypotheses regarding the absolute tension loss of the very stretched string jobs. My hypothesis is that you are losing a lot more tension than you think you are even after this prestretching. The feel might not change as much as compared to a regular string job, but that is a separate phenomenon than tension loss. I think playability arguments are often confounded with tension loss, but playability focused techniques are as interesting (if not moreso!) than tension focused techniques because that is what the player actually experiences.

As far as the permanent elongation comment, please read about material properties before making these claims:http://www.kazuli.com/UW/4A/ME534/lexan2.htm
If you have made any permanent elongation, you have absolutely affected the elastic properties of the string. It is naive (and very misleading!) to make a statement about the elastic elongation being hardly changed. This is for a thick piece of lexan (polycarbonate) plastic, but the principles still apply here.

I'd also like to point out to others to check out the deformation behavior section of the site. It is one reason why the stretch-ad-nauseum approach is an interesting one. Homogeneous materials can have interesting effects when stretched beyond the elastic limit/yield point that can affect playability in a large way. However, this doesn't say anything about preference or absolute "best."

Serious question as I can't find a definitive answer (although I recall reading about this in the past) - do strings really snap back faster than the ball leaves the string? Is a string bed a trampoline or is elasticity a non-factor in true energy return? Is it on the same order of magnitude as a stiff frame?

Is this amount of string deformation really "returning energy" as we think? I swear I saw some high speed footage years ago that suggested that strings do not snap back until after the ball leaves the frame, but I'm not able to find any articles now.

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Maybe the thread about elasticity started by ricardo is a good one for this topic?